請問， String prefix = fileName.substring(index);為什么不是 String prefix = fileName.substring(index+1);？？
public class HelloWorld {
??? public static void main(String[] args) {
?? ??? ?String fileName = "HelloWorld.jav";
?? ??? ?String email = "laurenyang@imooc.com";
?????????? ??? ?int index =fileName.lastIndexOf(".");
?? ??? ?String prefix = fileName.substring(index);
?? ??? ?if (?? index > 0 && (prefix.equals (".java"))) {
?? ??? ??? ?System.out.println("Java文件名正確");
?? ??? ?} else {
?? ??? ??? ?System.out.println("Java文件名無效");
?? ??? ?}
?? ??? ?int index2 = email.indexOf("@");?????? ?
?? ??? ?int index3 = email.indexOf('.');????? ?
?? ??? ?if (index2 != -1 && index3 > index2) {
?? ??? ??? ?System.out.println("郵箱格式正確");
?? ??? ?} else {
?? ??? ??? ?System.out.println("郵箱格式無效");
?? ??? ?}
?? ?}
}
??? public static void main(String[] args) {
?? ??? ?String fileName = "HelloWorld.jav";
?? ??? ?String email = "laurenyang@imooc.com";
?????????? ??? ?int index =fileName.lastIndexOf(".");
?? ??? ?String prefix = fileName.substring(index);
?? ??? ?if (?? index > 0 && (prefix.equals (".java"))) {
?? ??? ??? ?System.out.println("Java文件名正確");
?? ??? ?} else {
?? ??? ??? ?System.out.println("Java文件名無效");
?? ??? ?}
?? ??? ?int index2 = email.indexOf("@");?????? ?
?? ??? ?int index3 = email.indexOf('.');????? ?
?? ??? ?if (index2 != -1 && index3 > index2) {
?? ??? ??? ?System.out.println("郵箱格式正確");
?? ??? ?} else {
?? ??? ??? ?System.out.println("郵箱格式無效");
?? ??? ?}
?? ?}
}
2015-11-19
String prefix =fileName.toString(index+1,fileName.length);這段代碼啥意思了？
2015-08-25
因?yàn)?/p>
index的下標(biāo)從0開始